1. Field of the Invention
This invention relates to information setting devices for cameras having a dial-like selector by which photographic information such as shutter speeds, aperture values, or exposure modes are set in.
2. Description of the Prior Art
To allow for whatever shutter speed or aperture or any other exposure factor the photographer wishes to be set in the camera, there has been known a first method of setting shutter speeds or apertures all the way from the minimum to the maximum value in a single selector or dial operatively connected to a variable resistor having its resistance value related to the selected value of such exposure factor. Another method is that the variable resistor is replaced by a code plate with a scanner therefor to produce a corresponding digital output for the selected value of the exposure factor. Another or third method is by using two push buttons and a display. If the preliminarily set value on the display is different from a desired one, the photographer needs only to push either one or the other of the buttons to either step-up or step-down from the preliminary set value until the desired value appears in the display.
However, these prior known methods have large drawbacks. That is, in the first method, because, of its use of the variable resistor, an increase in the accuracy of increment of values, calls for high precision variable resistors. When employing commercially available variable resistors, therefore, it is necessary either to separate the good items from the bad, or to correct the resistance value of the used variable resistor by using an adjusting resistor. This leads to increases in the production cost. Another drawback is that to establish a high precision accuracy variable resistor, it is very difficult to locate the slider within required severe tolerances. The second method also has a drawback in that as the photographic information to be set in digital form is necessarily a word of usually not less than 3 bits, when the number of bits is intended to increase, the size of the electrode pattern of the coded plate unavoidably increases. Also to apply the output of the code plate to an exposure value computer, usually of IC form, there is a need to provide an equal number of output lines to the number of bits. In addition thereto, this unavoidably increase the number of pins of the IC, making it difficult to perform actual installation. For these reasons, the employment of the second method is not preferable to small size instruments, such as cameras. A common drawback of the first and second methods is that since all the numerical characters representing the available values of shutter time or aperture must be written on the dial, as the number of available values increases, the size of each of the numerical characters decreases so that it is difficult for the photographer to read the scale on the dial. This drawback is serious when whether or not the manageability is good, constitutes a large factor of appraisal as in cameras or like instruments. In the third method, due to the digital display, the two switches for the push buttons suffice for constructing the selector, giving a great advantage of simplifying its structure. In the case of the display within the viewfield of the finder of the camera, however, the photographer is obliged to do the work by using two fingers of his one hand under the condition that an additional finger of the same hand controlls the operation of the light metering start switch while looking through the finder. The third method also had a drawback that the selecting is a difficult operation. Particularly with cameras having a release button which also serves as the actuator for the aforesaid light metering start switch when it is pushed down to a first stroke where the display is also rendered operative, the photographer usually employs his index finger for actuation of the release button, and another finger for pushing the UP button or DOWN button. In doing so, it often happened that the release button is fully pushed down to a second stroke at a time during the photographic information selecting operation. Thereby an improper exposure results.
Attempts have been made to eliminate such drawbacks by techniques disclosed in Japanese Laid-Open patent applications Nos. SHO 58-63932 and SHO 58-63933, wherein use is made of two signals of different phase from each other, and the direction in which the photographic information selector is turned is detected by sensing the phases of the signals to perform addition or subtraction with the value set in the preceding selecting operation.
In the case of the technique disclosed in the above-identified patent applications, however, the selector has points in position at which either one or both of the aforesaid two signals changes or change their phases. When the selector is manually moved across any of these points, therefore, the setting of values of exposure factor is caused to suddenly shift. If the selector is handled in such a fashion as to swing clockwise and counter-clockwise past the point, the display changes for every time, giving a drawback that as it flickers, the efficiency of setting is hampered. Also due to chattering between the contacts of the switch, there is produced a similar problem. This problem is prominent particularly when the selector moves past each of the transit points of the set value, as the selector is operatively connected to mechanical switches. When in the manual exposure mode, such problem results in taking photographs of incorrect exposure.